Alcohol-induced susceptibility to pulmonary bacterial infections: A narrative review

Alcohol intake is widely accepted in diverse cultures around the world, although heavy and prolonged consumption can be harmful. Alcohol influences multiple organs through interorgan and intercellular signaling cascades. The common health conditions associated with alcohol use disorder (AUD) are pancreatitis, liver cirrhosis, neuropathies, cardiomyopathies, and dementia. By virtue of its anatomical orientation and function, the lung continually encounters microbes, and this can be exacerbated by excessive alcohol consumption. Alcohol abuse is a well-known risk factor for bacterial infection in the lung. Increased susceptibility to bacterial pneumonia is caused by impaired immune responses in individuals with AUD. The key cells to defend against pulmonary infections are innate immune cells, including alveolar macrophages, neutrophils, and adaptive immune cells, such as T and B cells. This review highlights recent advances illuminating the roles of innate immune responses in bacterial pneumonia and the effects of alcohol in bacterial pneumonia. Understanding the molecular mechanisms associated with innate immunity in the lung is essential for developing effective strategies to control pneumonia and alcohol-mediated immunosuppression.